Expanded polystyrene formwork for cast in place concrete structures

ABSTRACT

A formwork for use in constructing concrete structures is made out of expanded polystyrene coated with an epoxy hard coat on the surfaces of the formwork against which concrete is applied or poured in the construction of concrete structures. A method of making the formwork involves constructing the expanded polystyrene to a desired shape and applying the epoxy to the surfaces of the polystyrene to be used to contact concrete and allowing the epoxy to cure. A method of constructing concrete structures involves using the formwork described.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to Provisional Application Ser. No.60/493,114 filed Aug. 6, 2003, the disclosure of which is incorporatedby reference herein in its entirety, and to which priority is explicitlyclaimed herein to the filing date thereof.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention, in general, relates to the field of buildingconstruction. More precisely, the invention relates to the constructionof concrete structures using a new formwork. Specifically, the presentinvention relates to using a formwork composed of expanded polystyrene(EPS) coated with a two-part liquid epoxy hard coat for the constructionof concrete structures.

2. Discussion of the Related Art

Historically, builders have used formworks in the construction ofelevated concrete slabs and beams. For example, when forming an elevatedslab, concrete is poured on top of a formwork deck and over horizontallyprojected rebar (structural steel). The formwork deck is held in placeat the desired elevation by numerous methods. These include, but are notlimited to, scaffolding and wooden posts. Concrete columns and wallshave been poured previously in order to hold up the elevated deck andbeams. Upon sufficient curing of the concrete, the formwork is removedfrom below to leave a free-standing elevated concrete deck and beamsystem.

Currently, elevated concrete beam and slab systems are constructed usingformwork systems which are composed of plywood, steel, or fiberglass.Each of these methods is costly, and takes large amounts of work toinstall properly. Plywood formwork beam and slab systems are the easiestof the three. The finished surface left by plywood typically containswood grain impressions retained in the concrete from the wooden surfaceof the plywood sheets. This can be remedied by employing the use of highgrade plywood. However, this increases the cost tremendously. Steel pansare also used in the construction of beam and slab systems.

Steel pans are more expensive than using plywood decking. They are alsomuch larger in weight, making the man hours required for construction ofthe beam and slab system even higher. The finished surface that is leftby steel pans is better than that left by plywood decking. Fiberglassformwork for beam and slab systems is the most expensive means ofconstructing a concrete deck.

Fiberglass formwork is also much heavier than either plywood decking orsteel pans, and is an even more labor-intensive construction practice.The finished surface of the concrete, using fiberglass for formwork, istypically much better than that of both steel pans and plywood.

The possibility of reusing plywood, steel, and fiberglass varies.Plywood can be reused several times, with the finished surface of theconcrete decreasing in quality with each reuse. Plywood also demands theharvesting of valuable natural resources required for its production. Itcannot be recycled at the conclusion of its usefulness and must bedisposed of in landfills. Similarly, steel pans can be reused asformwork numerous times. Steel pans produce a finished surface on theconcrete that also diminishes with use of the steel pans. Steel pans,however, can be melted down for reuse at the end of a job. Fiberglassforms can typically be used for multiple pours for the duration of aconstruction project with minimal decline in the finished surface of theconcrete. However, at the conclusion of a construction projectfiberglass formwork cannot be recycled and must be disposed of.

With the current implementation of plywood, steel, or fiberglassformwork, there is a limit to the shapes which are attainable inconcrete construction. Irregular shapes, such as intricate curves, arenot an option using current construction methods.

An alternative approach more recently available from a company known asAlkus ((http://alkus.de/gb/NN_index.html) Aug. 3, 2004) involvesmanufacturing formwork panels out of polypropylene reinforced withaluminum or glass fiber mat. A problem with such panels is that they aredifficult to shape and suffer the same disadvantages and more than theaforementioned steel and fiberglass forms, and cannot be molded intointricate shapes.

SUMMARY OF THE INVENTION

The present invention is directed towards constructing a static mold orformwork structure. The mold may be used to form a building structuresuch as an elevated beam and slab system. A generally U-shape channelform is especially adapted to form a concrete beam for the system. Theslab is an outwardly extending section of concrete that is constructedat the same time as the beam. The system will be composed of a pluralityof beams. The system will typically contain horizontally extending rebar(structural steel reinforcement bars). The formwork is composed of acertain density of Expanded Polystyrene (EPS). The density will dependon the structural requirements for the safe construction of saidconcrete system. Ordinarily, it is anticipated that the formwork will bemade of two pound density expanded polystyrene. The EPS will be cut tothe desired shape, and placed into a restrained system in order topreclude movement occurring at the time of concrete placement. The EPSwill then be coated with a two-part epoxy/polyurethane enamel in orderto provide a finish currently unattainable with present Cast in Place(CIP) forming methods. When properly vibrated and placed, thepolyurethane “hard-coat” will leave the bottom surface (ceiling) of theelevated deck with a finish that will appear to be smooth and polished.This finish is currently unattainable solely with current formworkapproaches. Upon sufficient curing of the concrete, the EPS CIP formswill be removed for reuse, recycling, or disposal.

A primary object of the invention is to provide a cheaper means of castin place concrete construction. Another objective of the invention is toprovide the finished concrete surface with an appearance that will besmooth and polished. The EPS formwork will be much lighter than typicalwood, steel, or fiberglass decks, thus facilitating a construction cyclethat is much quicker in installation than is currently attainable inindustry. Another benefit of using EPS formwork is that it is recyclableafter construction use. EPS formwork will not contribute to refuse inlandfills, and does not require the use of valuable naturalresources—such as those required by steel and wood formwork. Anotherbenefit of using EPS formwork is the shapes which are currentlyunattainable in concrete cast in place construction. The EPS formworkcan be cut into intricate designs and then cast into the bottom, or“ceiling” of the concrete beam and slab system.

BRIEF DESCRIPTION OF THE DRAWINGS

Having briefly described the invention, the same will become betterunderstood from the appended drawings, wherein:

FIG. 1 is a perspective view representative of a formwork constructed inaccordance with the invention; and

FIG. 2 is an isometric cross-sectional view of the formwork of FIG. 1

DETAILED DISCUSSION

In accordance with the invention as illustrated in FIG. 1, a preferredembodiment of the formwork 11 includes a central portion 13 typicallymade of expanded polystyrene, while shown as a rectangular structure, itwill be appreciated by those of ordinary skill in the art that theformwork can be copied into intricate shapes as appropriate to theconcrete structure being poured or constructed. Once cut to the desiredshape, the formwork or formwork panel is placed into a restraint systemin order to preclude movement at the time of concrete placement orpouring. Prior to pouring the concrete, an epoxy polyurethane enamel isapplied on the surfaces which will be in contact with the concrete, andallowed to cure. Thereafter, the formwork is properly vibrated andplaced and the concrete poured. Upon sufficient curing of the concrete,the formwork is removed for reuse, recycling or disposal, and thepolyurethane hard coat leaves a smooth surface which appears to be bothsmooth and polished.

FIG. 2 illustrates in greater detail the formwork 11 of FIG. 1 shown incross-section. As may be appreciated, the center section 13 is made ofexpanded polystyrene may have on both upper and lower surfaces, forexample in the case where it is used to construct an elevated deck, theepoxy polyurethane enamel portions 15 can be both on the top and bottomside and used to leave the bottom surface, i.e. ceiling of an elevateddeck with a finish which appears to be smooth and polished.

In implementing the invention, specific types of expanded polyurethaneare used, for example, as described in Appendix A1- A6 entitled “TypicalPhysical Properties of Expanded Polystyrene for Use in the Formwork”,which follow and are part of the specification, are incorporated byreference herein, and are located before the claims.

Appendix A2 also compares the material used (polystyrene) for theinvention favorably relative to the use of plywood, and also describesother properties of the polystyrene material applicable for use in theinvention.

As will be appreciated by those of ordinary skill in the art, thisinformation is readily available from numerous websites such aswww.carpenter.com as of Aug. 3, 2004 and others.

In the case of the invention, the expanded polystyrene is shown havingcertain properties in the shaded area in Appendix A1 and identified astype II exhibiting a density (in pcf) of at least 1.35, and preferablyabout 1.35 to about 1.79 is most preferred for use in accordance withthe invention. While a preferred expanded polystyrene has beenidentified herein, it will be readily apparent to those of ordinaryskill in the art, that alternative types can be employed as may beappropriate to the particular or specific application, depending onstructural need and what is being built.

More specifically, in arriving at desired formwork load bearingcalculations, published ASTM methods were reviewed and used to arrive atthe desired load bearing calculations. More specifically, these ASTMmethods are described in the following ASTM international publications,the disclosures of which are specifically incorporated by referenceherein. The publications are as follows: Publication Title Designation:C 203-99 Standard Test Methods for Breaking Load and Flexural Propertiesof Block-Type Thermal Insulation Designation: C 578-03b StandardSpecification for Rigid, Cellular Polystyrene Thermal InsulationDesignation: D 732-02 Standard Test for Shear Strength of Plastics byPunch Tool Designation: D 1621-00 Standard Test Method for ComprehensiveProperties of Rigid Cellular Plastics Designation: D 1622-03 StandardTest for Apparent Density of Rigid Cellular Plastics Designation D1623-03 Standard Test Method for Tensile and Tensile Adhesion Propertiesof Rigid Cellular Plastics

With respect to the epoxy/polyurethane enamel employed in accordancewith the invention, one such enamel is available from Demand Products,Inc. under the name Liquid Rock. A Technical Data Sheet and MaterialSafety Data Sheet provide details about the specific material and isavailable form Demand Products, Inc. of Alpharetta, Ga. Morespecifically, a link to that company's website on the Internet isavailable at http://www.demandproducts.com andhttp://www.demandhotwire.com as of Aug. 3, 2004.

The material is a 2-component unfilled epoxy with low viscosity and goodflow qualities which can be applied over plastic foam surfaces where ahard, durable, and smooth coating is required. With respect to itsspecific properties, they are set forth in the following Tables: TABLE 1Encapsulant is a two-component, unfilled epoxy with low viscosity andflow quantities. Can be applied over plastic foam surfaces where a hard,durable, and smooth coating is required. Ratio Parts by Weight: 100Catalyst (Hardener):  16 Ratio Parts by Volume:  4.99 Catalyst(Hardener)  1 Room Temp., 72° F.:  20 mins. Cure: 2-3 hours Dry to touch   4-6 hours Dust-free     18 hours Through Cure*Pot Life 100 gram Mass*These times will change depending on volume and temperature.

TABLE 2 Physical Properties @ 72° F. Color: Off-white Shore “D” HardnessASTM D2240: 82 Viscosity, 5000 cps 2-component mix: Specific Gravity,1.30 2-component mix: Tensile Strength: 25000 psi ComprehensiveStrength: 40000 psi Maximum Use Temperature: 220° F. Shelf Life: 1 Year

Thus, as may be appreciated not only does the invention involve a newand integrated structure for formwork to be used in concreteapplications, there is also provided a method of making such formworkstructures. The method generally involves cutting a shape in a structuremade of expanded polystyrene into a desired shape for use in poured orapplied concrete applications. An epoxy polyurethane enamel is thenapplied to the surface of the expanded polystyrene which is to bearagainst poured or applied concrete. The enamel is allowed to cure andthe concrete is thereafter poured or applied to be in contact with theenamel. In a yet still further aspect, the invention involvesconstructing concrete structures using the formwork in accordance withthe invention by assembling the formwork as previously described,thereafter pouring or applying the concrete and when the concrete hassubstantially or sufficiently cured, removing the formwork to result ina concrete surface which appears smooth and polished.

Having thus generally described the invention, the same will becomebetter understood from the appended claims in which it is set forth in anon-limiting manner.

Appendix A1

typical physical properties of expanded polystyrene: Specificationreference: ASTM C578 Property Units ASTM Test Type XI Type I Type VIIIType II Type IX Density, Minimum pcf D1622 .7 .9 1.15 1.35 1.8 DensityRange pcf .70-.89  .90-1.14 1.15-1.34 1.35-1.79 1.80-2.20 StrengthProperties Compressive 10% Deformation psi D1621 5-9 10-14 13-18 15-2125-33 Flexural psi C203 10-18 25-30 32-38 40-50 55-75 Tensile psi D162314-18 16-20 17-21 18-22 23-27 Shear psi D732 11-13 18-22 23-25 26-3233-37 Shear Modulus psi 190-230 280-320 370-410 460-500 600-640 Modulusof Elasticity psi 110-150 180-220 250-310 320-360 460-500

R-Control EPS Fabricators Property Type XI Type I Type VIII Type II TypeIX Nominal Density, lb/ft³ (kg/m³) 0.75 (12) 1.00 (16) 1.25 (20) 1.50(24)  2.00 (32) Density¹, min., lb/ft³ (kg/m³) 0.70 (12) 0.90 (15) 1.15(18) 1.35 (22) 0.180 (29) Compressive strength¹ @10% def., min., psi   5  10   13   15   25 Flexural strength¹,   10   25   30   40   50¹See ASTM C-578 Standard Specification for complete information

Alliance of Foam Packaging Recyclers: Density (pcf) Strength PropertiesUnit 1 1.5 2 2.5 3 3.3 4 Stress @ 10% psi 13 24 30 42 64 67 80Compression Flexural Strength psi 29 43 58 75 88 105 125 TensileStrength psi 31 51 62 74 88 98 108 Shear Strength psi 31 53 70 92 118140 175

Pacemaker Plastics Corp. Property Type XI Type I Type VIII Type II TypeIX Nominal Density, lb/ft³ (kg/m³)  0.75 (12)  1.00 (16)  1.25 (20) 1.50 (24)  2.00 (32) Density¹, min., lb/ft³ (kg/m³)  0.70 (12)  0.90(15)  1.15 (18)  1.35 (22)  1.80 (29) Compressive strength¹ @10% def.,min., psi (kPa)   5.0 (35)  10.0 (69)  13.0 (90)  15.0 (104)  25.0 (173)Flexural Strength¹, min., psi (kPa)  10.0 (69)  25.0 (173)  30.0 (208) 40.0 (276)  50.0 (345) Compressive Resistance² @1% deformation, min.,kPa (psi)  22 (3.2)  32 (4.6)  43 (6.2)  57 (8.3)  82 (11.9) Modulus ofElasticity², min., kPa (psi) 2200 (319 3200 (464) 4300 (624) 5700 (827)8200 (1189)Pacemaker Expanded Polystyrene (EPS) Properties per ASTM C 578 and ULTestsAppendix A2

Published Properties Specification reference: ASTM C578 Property UnitsASTM Test Type XI Type I Type VIII Type II Type IX Density, Minimum pcfD1622 .7 .9 1.15 1.35 1.8 Density Range pcf .70-.89  .90-1.14 1.15-1.341.35-1.79 1.80-2.20 Strength Properties Compressive 10% Deformation psiD1621 5-9 10-14 13-18 15-21 25-33 Flexural psi C203 10-18 25-30 32-3840-50 55-75 Tensile psi D1623 14-18 16-20 17-21 18-22 23-27 Shear psiD732 11-13 18-22 23-25 26-32 33-37 Shear Modulus psi 190-230 280-320370-410 460-500 600-640 Modulus of Elasticity psi 110-150 180-220250-310 320-360 460-500

Minimum Properties Specification reference: ASTM C578 Property UnitsASTM Test Type XI Type I Type VIII Type II Type IX Density, Minimum pcfD1622 .7 .9 1.15 1.35 1.8 Density Range pcf .70-.89 .90-1.14 1.15-1.341.35-1.79 1.80-2.20 Strength Properties Compressive 10% Deformation psiD1621 5 10 13 15 25 Flexural psi C203 10 25 32 40 55 Tensile psi D162314 16 17 18 23 Shear psi D732 11 18 23 26 33 Shear Modulus psi 190 280370 460 600 Modulus of Elasticity psi 110 180 250 320 460

Plywood Properties Strength Properties Compressive 10% Deformation psi210 Flexural psi 1545 Shear psi 57 Modulus of Elasticity psi 1500000

Plywood Properties for 12″ Nominal Width Nominal Thickness I S lb/Q inin{circumflex over ( )}4 in{circumflex over ( )}3 in{circumflex over( )}2 ¼ 0.008 0.059 2.01 ⅜ 0.027 0.125 3.088 ½ 0.077 0.236 4.466 ⅝ 0.1290.339 5.2824 ¾ 0.197 0.412 6.762 ⅞ 0.278 0.515 8.05 1 0.423 0.664 8.8821⅛ 0.548 0.82 9.883Appendix A3

Properties of a 12″ Wide Rectangluar Section Ht. c I S Q lb/Q (in) (in)(in{circumflex over ( )}4) (in{circumflex over ( )}3) (in{circumflexover ( )}3) (in{circumflex over ( )}2) 0.5 0.25 0.125 0.5 0.375 4 1 0.51 2 1.5 8 1.5 0.75 3.375 4.5 3.375 12 2 1 8 8 6 16 2.5 1.25 15.625 12.59.375 20 3 1.5 27 18 13.5 24 3.5 1.75 42.875 24.5 18.375 28 4 2 64 32 2432 4.5 2.25 91.125 40.5 30.375 36 5 2.5 125 50 37.5 40 5.5 2.75 166.37560.5 45.375 44 6 3 216 72 54 48 6.5 3.25 274.625 84.5 63.375 52 7 3.5343 98 73.5 56 7.5 3.75 421.875 112.5 84.375 60 8 4 512 128 96 64 8.54.25 614.125 144.5 108.375 68 9 4.5 729 162 121.5 72 9.5 4.75 857.375180.5 135.375 76 10 5 1000 200 150 80 10.5 5.25 1157.625 220.5 165.37584 11 5.5 1331 242 181.5 88 11.5 5.75 1520.875 264.5 198.375 92 12 61728 288 216 96 12.5 6.25 1953.125 312.5 234.375 100 13 6.5 2197 338253.5 104 13.5 6.75 2460.375 364.5 273.375 108 14 7 2744 392 294 11214.5 7.25 3048.625 420.5 315.375 116 15 7.5 3375 450 337.5 120 15.5 7.753723.875 480.5 360.375 124 16 8 4096 512 384 128 16.5 8.25 4492.125544.5 408.375 132 17 8.5 4913 578 433.5 136 17.5 8.75 5359.375 612.5459.375 140 18 9 5832 648 486 144 18.5 9.25 6331.625 684.5 513.375 14819 9.5 6859 722 541.5 152 19.5 9.75 7414.875 760.5 570.375 156 20 108000 800 600 160 20.5 10.25 8615.125 840.5 630.375 164 21 10.5 9261 882661.5 168 21.5 10.75 9938.375 924.5 693.375 172 22 11 10648 968 726 17622.5 11.25 11390.63 1012.5 759.375 180 23 11.5 12167 1058 793.5 184 23.511.75 12977.88 1104.5 828.375 188 24 12 13824 1152 864 192 24.5 12.2514706.13 1200.5 900.375 196 25 12.5 15625 1250 937.5 200 25.5 12.7516581.38 1300.5 975.375 204 26 13 17576 1352 1014 208 26.5 13.2518609.63 1404.5 1053.375 212 27 13.5 19683 1458 1093.5 216 27.5 13.7520796.88 1512.5 1134.375 220 28 14 21952 1568 1176 224 28.5 14.2523149.13 1624.5 1218.375 228 29 14.5 24389 1682 1261.5 232 29.5 14.7525672.38 1740.5 1305.375 236 30 15 27000 1800 1350 240 30.5 15.2528372.63 1860.5 1395.375 244 31 15.5 29791 1922 1441.5 248 31.5 15.7531255.88 1984.5 1488.375 252 32 16 32768 2048 1536 256 32.5 16.2534328.13 2112.5 1584.375 260 33 16.5 35937 2178 1633.5 264 33.5 16.7537595.38 2244.5 1683.375 268 34 17 39304 2312 1734 272 34.5 17.2541063.63 2380.5 1785.375 276 35 17.5 42875 2450 1837.5 280 35.5 17.7544738.88 2520.5 1890.375 284 36 18 46656 2592 1944 288 36.5 18.2548627.13 2664.5 1998.375 292 37 18.5 50653 2738 2053.5 296 37.5 18.7552734.38 2812.5 2109.375 300 38 19 54872 2888 2166 304 38.5 19.2557066.63 2964.5 2223.375 308 39 19.5 59319 3042 2281.5 312 39.5 19.7561629.88 3120.5 2340.375 316 40 20 64000 3200 2400 320 40.5 20.2566430.13 3280.5 2460.375 324 41 20.5 68921 3362 2521.5 328

Appendix A4 Plyform B-B Class 1 (Strong with Span) Nominal F′b = 1545psi (for 12″ width) Nominal Thickness S S * F′b S * F′b (in.)(in{circumflex over ( )}3) (in.-lb.) (ft.-lb) ¼ 0.059 91.16 7.60 ⅜ 0.125193.13 16.09 ½ 0.236 364.62 30.39 ⅝ 0.339 523.76 43.65 ¾ 0.412 636.5453.05 ⅞ 0.515 795.68 66.31 1 0.664 1025.88 85.49 1⅛ 0.82 1266.90 105.58

Type II Foam Allowable F′b = 10 psi (for 12″ width) (Fb = 40 psi ::Safety Factor of 4) Nominal Thickness S S * F′b S * F′b (in.)(in{circumflex over ( )}3) (in.-lb.) (ft.-lb) 2 8 80 6.67 2.5 12.5 12510.42 3 18 180 15.00 3.5 24.5 245 20.42 4 32 320 26.67 4.5 40.5 40533.75 5 50 500 41.67 5.5 60.5 605 50.42 6 72 720 60.00 6.5 84.5 84570.42 7 98 980 81.67 7.5 112.5 1125 93.75 8 128 1280 106.67 8.5 144.51445 120.42 9 162 1620 135.00 9.5 180.5 1805 150.42 10 200 2000 166.67

Moment Resistance (Flexural Strength Comparison) Needed Weight NeededGiven Plywood per Type II Weight per Weight Savings Moment Thickness sq.foot Thickness Sq. Foot Per 100 Sq. Ft. (ft.-lb) (in.) lbs. (in.) lbs.(lbs.) 5 ¼ 0.80 2 0.23 58 10 ⅜ 1.10 2.5 0.28 82 15 ⅜ 1.10 3 0.34 76 20 ½1.50 3.5 0.39 111 25 ½ 1.50 4 0.45 105 30 ½ 1.50 4.5 0.51 99 35 ⅝ 1.80 50.56 124 40 ⅝ 1.80 5 0.56 124 50 ¾ 2.20 5.5 0.62 158 60 ⅞ 2.60 6 0.68193 70 1 3.00 6.5 0.73 227 80 1 3.00 7 0.79 221 90 1⅛ 3.30 7.5 0.84 246100 1⅛ 3.30 8 0.90 240

Appendix A5 Plyform B-B Class 1 (Strong with Span) Nominal F′v = 57 psi(for 12″ width) Nominal Thickness lb/Q lb/Q * F′v = V_(allowed) (in.)Rolling Shear (in.{circumflex over ( )}2) (lbs.) ¼ 2.01 114.57 ⅜ 3.088176.02 ½ 4.466 254.56 ⅝ 5.2824 301.10 ¾ 6.762 385.43 ⅞ 8.05 458.85 18.882 506.27 1⅛ 9.883 563.33

Type II Foam Allowable F′v = 6.5 psi (for 12″ width, Fv = 26 psi ::Safety Factor of 4) Nominal lb/Q Thickness Rolling Shear Equivalentlb/Q * F′v = V_(allowed) (in.) (in.{circumflex over ( )}2) (lbs.) 2 16104 2.5 20 130 3 24 156 3.5 28 182 4 32 208 4.5 36 234 5 40 260 5.5 44286 6 48 312 6.5 52 338 7 56 364 7.5 60 390 8 64 416 8.5 68 442 9 72 4689.5 76 494 10 80 520 10.5 84 546 11 88 572

Appendix A5 Shear Resistance (Shear Strength Comparison) Given NeededWeight Needed Weight Shear Plywood per sq. Type II Weight per Sq.Savings Per Load Thickness foot Thickness Foot 100 Sq. Ft. (lbs) (in.)lbs. (in.) lbs. (lbs.) 100 ¼ 0.80 2 0.225 58 125 ⅜ 1.10 2.5 0.281 82 150⅜ 1.10 3 0.338 76 175 ⅜ 1.10 3.5 0.394 71 200 ½ 1.50 4 0.450 105 225 ½1.50 4.5 0.506 99 250 ½ 1.50 5 0.563 94 275 ⅝ 1.80 5.5 0.619 118 300 ⅝1.80 6 0.675 113 350 ¾ 2.20 7 0.788 141 400 ⅞ 2.60 8 0.900 170 450 ⅞2.60 9 1.013 159 500 1 3.00 10 1.125 188 550 1⅛ 3.30 11 1.238 206

Appendix A6 Plyform B-B Class 1 (Strong with Span) Nominal E = 1500000psi (for 12″ width) Nominal Thickness I Flexural Stiffness El (in.)(in.{circumflex over ( )}4) (lbs-in{circumflex over ( )}2) ¼ 0.00812,000 ⅜ 0.027 40,500 ½ 0.077 115,500 ⅝ 0.129 193,500 ¾ 0.197 295,500 ⅞0.278 417,000 1 0.423 634,500 1⅛ 0.548 822,000

Type II Foam Allowable E = 320 psi (for 12″ width, E = 320 :: No SafetyFactor for Deflection) Nominal Thickness I Flexural Stiffness EI (in.)(in.{circumflex over ( )}4) (lbs-in{circumflex over ( )}2) 2 8 2,560 2.515.625 5,000 3 27 8,640 3.5 42.875 13,720 4 64 20,480 4.5 91.125 29,1605 125 40,000 5.5 166.375 53,240 6 216 69,120 6.5 274.625 87,880 7 343109,760 7.5 421.875 135,000 8 512 163,840 8.5 614.125 196,520 9 729233,280 9.5 857.375 274,360 10 1000 320,000 10.5 1157.625 370,440 111331 425,920 11.5 1520.875 486,680 12 1728 552,960 12.5 1953.125 625,00013 2197 703,040 13.5 2460.375 787,320 14 2744 878,080

Appendix A6 Deflection Comparison for Given Stiffness Needed WeightNeeded Weight Weight Given Stiffness Plywood per sq. Type II per Sq.Savings Per Requirement Thickness foot Thickness Foot 100 Sq. Ft. (EI =lbs-in{circumflex over ( )}2) (in.) lbs. (in.) lbs. (lbs.) 10,000 ¼ 0.803.5 0.394 41 40,000 ⅜ 1.10 5 0.563 54 50,000 ½ 1.50 5.5 0.619 88 75,000½ 1.50 6.5 0.731 77 100,000 ½ 1.50 7 0.788 71 150,000 ⅝ 1.80 8 0.900 90200,000 ¾ 2.20 9 1.013 119 250,000 ¾ 2.20 9.5 1.069 113 300,000 ⅞ 2.6010 1.125 148 400,000 ⅞ 2.60 11 1.238 136 500,000 1 3.00 12 1.350 165600,000 1 3.00 12.5 1.406 159 700,000 1⅛ 3.30 13 1.463 184 800,000 1⅛3.30 14 1.575 173

1. A formwork for cast in place concrete structures, comprising: aformwork structure made of expanded polystyrene; and an enamel coatingon at least one surface of said formwork to be in contact with poured orapplied concrete which will make up at least a part of a concretestructure.
 2. The formwork of claim 1, wherein said expanded polystyrenehas a density of at least about 1.35 pcf.
 3. The formwork of claim 2,wherein said expanded polystyrene has a density of at least about 1.35pcf to about 1.79 pcf.
 4. The formwork of claim 1, wherein the strengthproperties of said expanded polystyrene comprises: Compressive 10%Deformation Strength of at least about 15 psi; Flexural Strength of atleast about 40 psi; Tensile Strength of at least about 18 psi; ShearStrength of at least about 26 psi; Shear Modulus of at least about 460psi; and Modulus of Elasticity of at least about 320 psi.
 5. Theformwork of claim 1, wherein the strength properties of said expandedpolystyrene comprises: Stress at 10% Compression of at least about 30psi; Flexural Strength of at least about 58 psi; Tensile Strength of atleast about 62 psi; and Shear Strength of at least about 70 psi.
 6. Theformwork of claim 1, wherein the enamel coating is polyurethane.
 7. Theformwork of claim 6, wherein the polyurethane coating is made from a twocomponent unfilled epoxy mixed with a catalytic hardener, the resultingpolystyrene having tensile strength properties of about 25,000 psi andcomprehensive strength properties of about 40,000 psi.
 8. A method ofmanufacturing a formwork for cast in place concrete structures,comprising: shaping a piece of expanded polystyrene into a predeterminedformwork shape; applying an enamel coating on at least one surface ofsaid formwork to be in contact with poured or applied concrete; andcuring the enamel coating.
 9. A method of manufacturing a concretestructure comprising: shaping a piece of expanded polystyrene into apredetermined formwork shape; applying an enamel coating on at least onesurface of said formwork to be in contact with poured or appliedconcrete; curing the enamel coating; applying or pouring concrete intocontact with the cured enamel coating to have the concrete assume adesired shape; allowing the concrete to cure; and removing the formworkafter the concrete has cured sufficiently to result in at least aportion of a concrete structure.